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Across 1. series of genes that controls the organs and tissues that develop in various parts of an embryo 4. decoding of a mRNA message into a polypeptide chain 6. group of three bases ona tRNA molecule that are complementary to an mRNA codon 8. virus that infects bacteria 11. change in a DNA sequence that affects genetic imformation 12. process in which one strain of bacteria is changed by a gene or genes from another strain of bacteria 15. copying process by which a cell duplicates its DNA 19. intervening sequence of DNA; does not code for a protein 20. mutation that affects a single nucleotide, usually by substituting one nucleotide for another 21. enzyme that "proofreads" new DNA strands, helping to ensure that each molecule is a nearly perfect copy of the original DNA 22. region of DNA that indicates to an enzyme where to bind to make RNA 24. type of RNA molecule that transfers amino acids to ribosomes during protein synthesis 25. principle that bonds in DNA can form only between adenine and thymine and between guanine and cytosine

Down 2. monomer of nuceic acids made up of a 5-carbon sugar, a phosphate group, and a nitrogenous base 3. mutation that shifts the "reading" frame of the genetic message by inserting or deleting a nucleotide 5. process in which part of the nucleotide sequence of DNA is copied into a complementary sequence in RNA 7. RNA molecule that carries copies of instructions for the assemble of amino acids into proteins from DNA to the rest of the cell 9. group of genes operating together 10. enzyme similar to DNA polymerase that binds to DNA and seperates the DNA strands during transcription 13. granular material visible within the nuceus; consists of DNA tightly coiled around proteins 14. expressed sequence of DNA; codes for a protein 16. type of RNA that makes up the major part of ribosomes 17. region of chromosome in an operon to which the repressor binds when the operon is "turned off" 18. globular protein molecule around which DNA is tightly coiled in chromatin 23. three-nucleotide sequence on messenger RNA that codes for a single amino acid